Meh, was bored, and drew bubbles for an undersea pic a bit ago o: And so I decided to do a tutorial for it. c: So, this is to do bubbles in Java, hence title.
First, color the background black. Make sure everywhere on the canvas is black, and there are no white spots. (I suppose)
Then take your fave color, or any random color, use airbrush, size 100 and Opacity 34-50 c: Or whichever you think would work better.
After that, you then create a new layer, use the color white and then pen tool to make different sized circles. Make however many suit you and how big or small you want them.
Lock the alpha on the layer with the circles, use the watercolor tool with the Opacity at 34, and size between 10 and 20, use the background color, and start coloring in the middle of the circle until it looks like the image, make sure to keep a white lining.
Then continue using watercolor tool, but with white, and with the size at 5. Then stroke lightly at the top, to look like the image, yes, it's suppose to look blended.
Continue using the same size, and the watercolor tool, also white to go around the top of the lining, near the top shine.
Just do that to the others, and there you have it. c: Hope this helps. .maybe. xD